Stem cells are undifferentiated cells having the ability to differentiate into two or more cell types with self-replication ability. Stem cells can be classified into totipotent stem cells, pluripotent stem cells, and multipotent stem cells depending upon differentiation potency thereof. In addition, stem cells can be classified into embryonic stem cells and adult stem cells depending upon biological origin. While embryonic stem cells are derived from preimplantation embryos, fetal reproductive organs in various stages of development, and the like, adult stem cells are derived from each organ, e.g., bone marrow, brain, liver, pancreas, or the like, of adults.
Recently, preclinical and clinical research to apply stem cells to various diseases, such as cerebral infarctions, traumatic brain injuries, and musculoskeletal diseases, is underway. However, current technology is merely focused on simply isolation, culture/proliferation and injection of stem cells. In addition, recent clinical research results show that such stem cell therapies do not exhibit distinct effects yet. Accordingly, research on various gene-modified stem cells to increase therapeutic effects is underway. However, application of cell therapy, in which genes are modified, to the human body is limited due to ethical problems.
In addition, there are several problems in applying therapeutic methods using stem cells to clinical trials. For example, tumor masses may be formed after engraftment of stem cells to organs, and cerebral infarction may occur due to an artery occlusion likely induced by the large size of stem cell itself. The stem cells easily move into the brain when the brain-blood vessel barrier is open as in an acute phase. However, in a chronic phase, movement of the stem cells is limited due to large sizes thereof.
Meanwhile, cerebrovascular diseases are neurologic deficits due to a problem in blood supply to the brain. Examples of cerebrovascular diseases include stroke, cerebral infarction, cerebral hemorrhage, cerebral arteriosclerosis, subarachnoid hemorrhage, cerebral thrombosis, cerebral embolism, etc.
Recently, a low birthrate is one of the most serious national problems. With regard to this, delivery of premature babies due to an increase in the average age of pregnant women and the application of the assisted reproductive technique due to increased infertility are remarkably increasing. The most important factor determining the quality of life of premature babies is a cranial nerve development state after treatment. With regard to this, intraventricular hemorrhage (IVH) in premature infants generally occurs within one week after birth and is a most important and dangerous disease that causes severe diseases including cerebral palsy, mental retardation, hearing loss, vision loss, and the like, as well as hydrocephalus, after bleeding. Bleeding into the cerebral ventricle causes damage to neighboring immature brain tissue and hydrocephalus after bleeding, thereby causing severe brain damage. However, there is, as yet, no definite remedy for intraventricular hemorrhage, and thus, it is a very important and urgent task to develop a remedy for treating premature babies.
Although research to develop drugs for treating cerebrovascular diseases has been actively underway, there is, as yet, no absolutely disclosure about a relation between cerebrovascular diseases, particularly the intraventricular hemorrhage, and stem cell-derived exosomes.